1) Field
This disclosure relates to a carbon/epoxy resin composition and a method of producing a carbon-epoxy dielectric layer using the same.
2) Description of the Related Art
A passive device, such as a register, a capacitor, an inductor, etc. is embedded in a printed circuit board (“PCB”) to decrease the surface area of the board so that a resulting device may have reduced size and weight. In addition, when a passive device is embedded in a PCB, inductance may be decreased, improving electrical performance, and the number of solder joints is decreased, improving the reliability of the device and reducing cost.
An embedded capacitor, which is one example of a passive device, may have a capacitance of 1 picofarad (pF) to 1 microfarad (μF) or more depending upon the application.
It is possible to provide a thin capacitor having a high capacitance by using a thin film process such as sputtering, chemical vapor deposition (“CVD”) or the like. However, a thin film process has a drawback in that it is difficult to perform at a low temperature, a ceramic thin film is fragile when it is applied to an organic board and the cost of the manufacturing process is high. Therefore, it is difficult to commercialize such a capacitor by applying sputtering or CVD to an organic board, such as an epoxy board, for example an FR-4 board, or a flexible board.
A polymer thick film process is an inexpensive process and is reliable when used with an organic board, but it has a drawback in that the resulting film has low dielectric capacity.
Recently, there have been many attempts to overcome the drawbacks of thin film processes, use the advantages of thick film processes and achieve high capacitance by dispersing conductive particles, such as metal or carbon black particles, in a thermosetting polymer matrix and adjusting the concentration thereof around the percolation threshold.
Currently, a carbon black polymer composite having a high dielectric constant is obtained by including an imidazole-based curing catalyst and carbon black as a conductive material. In this case, the imidazole-based catalyst may be poisoned by the carbon black. As the result, the carbon black-polymer composite has a high dielectric constant, but the polymer matrix is less cured so the general dielectric loss ratio is increased, making commercialization difficult.
Accordingly, a new method of decreasing the dielectric loss ratio, by improving thermal stability and increasing a degree of curing, by further adding an organic acid to the carbon black-polymer composite to decrease the poisoning, is being developed. However, the dielectric loss ratio when an organic acid is added is decreased too little, making commercialization difficult.